Trespass upon real property is defined, generally speaking, as the act of going upon the real property of another without his consent or express or implied invitation. When trespass is proved, it can constitute a crime or a defense to a civil action. In dog bite cases, the issue of trespass arises most often when the victim is bitten on privately owned property.
The victim who was bitten on private property therefore must always establish that he had a right to be there. Examples of an explicit right are a leasehold interest in the property, or an explicit invitation such as when one is an invited guest at a party. Examples of implicit invitations include but are not limited to:
- Neighbors who customarily enter each other's yards and even homes without prior notice.
- Children who often play in a front yard or a back yard.
- A customer who enters a store that is open for business.
There are many other situations where a person will not be regarded as a trespasser. See Defenses - Trespass by U.S. Legal.
If the victim is a trespasser, the next issue is whether the dog was known to be vicious. The owner, harborer or keeper of a vicious dog is not permitted to use the defense of trespass against a dog bite victim. The rule is stated in Restatement, Second, Torts § 338 (1965):
A possessor of land who is in immediate control of a force, and knows or has reason to know of the presence of trespassers in dangerous proximity to it, is subject to liability for physical harm thereby caused to them by his failure to exercise reasonable care (a) so to control the force as to prevent it from doing harm to them, or (b) to give a warning which is reasonably adequate to enable them to protect themselves.
See the discussion in Farrier v. Payton (1977) 562 P.2d 779, 785-786.
Most dog bite statutes incorporate the trespass defense. See, for example, the California dog bite statute and Fullerton v. Conan (1948) 87 Cal.App.2d 354 (against clear prohibition by dog owner, young child opened a gate and wandered into dog owner's back yard while she and her mother were guests; held that the child was trespassing and therefore no liability under the dog bite statute). For that reason, a dog bite victim who was bitten while trespassing should not base his claim upon the state's dog bite statute, but on the common law ground of scienter (i.e., the one bite rule). For more about the distinctions between dog bite statutes and scienter, see Legal Right of Dog Bite Victims in the USA and The One Bite Rule.